Electrical conductors and insulated cables comprising the same

ABSTRACT

AN ELECTRICAL CONDUCTOR WITH IMPROVED TOUGHNESS AND WORKABILITY IS MADE BY ADDING ABOUT 0.01% TIN TO HIGHIRON COTENT, ZINC BEARING ALUMINUM TO BE HOT-ROLLED FROM CAST BARS. INSULATED CABLES ARE MADE COMPRISING THE IMPROVED CONDUCTORS.

April 1974 I D. s. MEDlCK ETAL. 3,806,326

ELECTRICAL CONDUCTORS AND INSULATED CABLES COMPRISING THE SAME Filed May24, 1971 I N VEN I 0R3 D. S. MEDRICK C. J. SNYDER and d ETEAGUE UnitedStates Patent O U.S. Cl. 29183-5 7 Claims ABSTRACT OF THE DISCLOSURE Anelectrical conductor with improved toughness and workability is made byadding about 0.01% tin to highiron content, zinc bearing aluminum to behot-rolled from cast bars. Insulated cables are made comprising theimproved conductors.

BACKGROUND OF THE INVENTION In Pat. 3,063,832, dated Nov. 13, 1962, C.J. Snyder, one of the applicants in the present case, disclosed a veryhigh purity aluminum conductor in which the conductivity was maintainedabove 62% of the International Annealed Copper Standard (IACS) by theaddition of tin. However, it was believed at that time that in order toachieve the advantage of the tin addition the aluminum content wouldhave to be at least 99.5% and preferably 99.6%. Such high purityaluminum, is, however unduly expensive. R. J. Schoerner, in Pat.3,512,221, issued May 19, 1970, taught the use in continuous cast bar ofa high iron content aluminum for which he claimed superior elongation.We have found that high iron aluminum without the presently discoveredaddition of tin is deficiently brittle in such operations as compactingand does not provide consistent 62% conductivity in the V2 hard or fullyannealed state.

SUMMARY We have invented an electric conductor which may take the formof bare rod suitable for cold drawing having a diameter of 0.25 to 1.00inch, cold drawn wires, or standed pluralities of such wires, but is notlimited thereto, and which has minimum 62% IACS conductivity at a 16,000p.s.i. tensile strength, consisting essentially of 99.3 to 99.5 weightpercent aluminum, 0.3 to 0.45 weight percent iron, at least 0.01 weightpercent tin, at least 0.02 weight percent zinc, and the remainderimpurities normally present in aluminum of electrical conductivitygrade. We have also invented insulated conductors comprising the colddrawn wire of our invention and insulated cables comprising such wires.In making the conductor of our invention we prefer a method whereby aningot is cast having the above composition, followed by cooling theentire mass to room temperature. The ingots are subsequently reheated toat least 600 F. and hot rolled to red having a diameter between 14 inchand 1 inch.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a pictorial view of acable made to our invention.

FIG. 2 shows a diagram of the steps of a method of our invention.

FIG. 3 shows a pictorial view of an insulated wire made to ourinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Example 1 Analysis byWeight: 0.058% silicon, 0.420% iron, 0.019% copper, 0.005% manganese,0.015% boron,

3,806,326 Patented Apr. 23, 1974 0.002% vanadium, 0.001% chromium,0.030% zinc, .009% nickel, 0.005% tin, 99.436% aluminum, by difference.

The aluminum of Example 1 was prepared by melting an EC grade aluminumand adding tin to bring the tin content to 0.01%. Thereafter the metalwas melted in a crucible 11 (FIG. 2) poured into a mold 12 to form aningot 13. A large number of the ingots 13 were stored for periods oftime suflicient for them to come to room temperature and were stored atroom temperature until needed. Thereafter the ingots 13 were transportedto a rolling mill where they were heated in a preheating oven 14 to 650F. From the oven 14 the ingots passed through a hot rolling mill 16,emerging therefrom as a rod 17 having a diameter from about 0.25 to 1.00inch.

The rod 17 is subsequently cold drawn in a conventional manner to form awire conductor 18 which may be insulated as shown in FIG. 3 with enamel19 or with an extruded plastic, or stranded with other wires into astranded conductor 21, insulated, and formed with other such insulatedstrands, into a cable 22.

When the conductor of Example 1 drawn to #12 AWG was batch annealed tohalf hard temper the following tensile and elongation measurements weremade on three specimens: 15,730 p.s.i. and 19.5%, 16,100 p.s.i. and18.0%, 16,300 p.s.i. and 20.0%. Conductivity of all specimens exceeded62% IACS. A creep test was conducted by holding a specimen under aconstant 10,000 p.s.i. tensile load for 833 hours at room temperature.The total extension so determined was 240 microinches per inch ascompared to typical values of 2200 microinches per inch for EC gradealuminum extended similarly for 500 hours.

Example 2 Analysis by weight: 0.057% silicon, 0.440% iron, 0.015 copper,0.005% manganese, 0.006% boron, 0.001% magnesium, 0.003% vanadium,0.001% titanium, 0.001% chromium, 0.022% zinc, 0.011% nickel, 0.007%tin, 99.431% aluminum, by difference.

Conductor of Example 2 was cold drawn to #12 AWG and specimens found tohave tensile strengths and elongation as follows after continuousannealing: 1 8,048 p.s.i. and 11.0%, 18,400 p.s.i. and 15.5%, 18,196p.s.i. and 12.0%, 18,196 p.s.i. and 11.8%, 16,840 p.s.i. and 16.2%,16,840 p.s.i. and 16.0%. Additional conductor was cold drawn to #10 AWG,continuously annealed, and found to have tensile strengths andelongation of 15,570 p.s.i. and 18.2%, and 16,060 p.s.i. and 12.0%.Conductivity was in excess of 62% IACS.

Example 3 Analysis by weight: 0.058% silicon, 0.420% iron, 0.019%copper, 0.005% manganese, 0.015% boron, 0.002% vanadium, 0.001%chromium, 0.030% zinc,

0.009% nickel, 0.005% tin, 99.436% aluminum, by difference.

Conductor of Example 3 was cold drawn to #10 and #12 AWG. Conductor wascold drawn to 0.097 in diameter, seven-stranded together and compactedto 2/ 0 AWG. No cracking was experienced during compacting. Wire drawnto 0.0975 inch diameter was annealed /2 hard and specimens found to havethe following tensile strengths and elongation: 16,540 p.s.i. and 13.4%,15,970 p.s.i. and 15.8%, 16,140 p.s.i. and 18.2%, 16,270 p.s.i. and16.7%, 1 6,600 p.s.i. and 11.7%, 16,270 p.s.i. and 13.5%. Theconductivity exceeded 62% IACS.

Example 4 Analysis by weight: 0.051% silicon, 0.437% iron, 0.016%copper, 0.006% manganese, 0.010% boron, 0.002% magnesium, 0.001%vanadium, 0.027% zinc,

3 0.004% nickel, 0.005% tin, 99.44l% aluminum, by difference.

Conductor of Example 4 was hard drawn to #13 and 19.5 AWG for use asmagnet wire. In the hard drawn condition conductivity exceeded 62% IACSand after soft annealing the elongation was at least 23%.

Example 5 Analysis by weight: 0.053% silicon, 0.430% iron, 0.016%copper, 0.006% manganese, 0.011% boron, 0.002% magnesium, 0.002%vanadium, 0.028% zinc, 0.004% nickel, 0.007% tin, 99.441% aluminum, bydifference.

Conductor of Example 5 was hard drawn to #13 and #19.5 AWG magnet wire.In the hard drawn condition the conductivity exceeded 62%, and aftersoft annealin the elongation was at least 23%.

Example 6 Analysis by weight: 0.055% silicon, 0.391% iron, 0.014%copper, 0.004% manganese, 0.006% boron, 0.001% magnesium, 0.001%vanadium, 0.001% titanium, 0.001% chromium, 0.025% zinc, 0.009% nickel,0.010% tin, 99.482% aluminum, by difierence.

Conductor of Example 6 was'hard drawn into commercially useful wire,with electrical conductivity of 62% in the annealing condition.

The wire cold drawn in Examples 2-6 was all first cast into ingots,permitted to cool, reheated to at least 600 F., and hot rolled into rodprior to cold drawing. We believe that the cooling and reheating steps,when applied to the iron, zinc, tin bearing aluminum of our inventionhas a hitherto unsuspected effect, the exact mechanism of which isunknown that influences the toughness, high elongation, workability,high conductivity, and very low creep of our conductor. The toughnessand workabilityare manifested by excellent performance of our conductorduring manufacturing operations where it can be flipped over from onereel to another in high-speed wire drawing, without breaking and can becompacted readily without cracking.

We have invented a new conductor, composition, and

. 4 than definitive and for which-we desire an award of Letters Patentas defined in the following claims.

We claim:

1. A drawn electric conductor annealed to half-hard temper, having aminimum conductivity at a tensile strength of 16,000 p.s.i. of 62% ofthe International Annealed Copper Standard, consisting essentially of99.3 to 99.441 weight percent aluminum, 0.3 to 0.45 Weight percent iron,at least about 0.005 weight percent tin, at least 0.02 weight percentzinc and the remainder impurities normally present in aluminum ofelectrical conductivity grade, the amounts of each of said elementsbeing so selected that said drawn and annealed conducvtor, held under aconstant 10,000 p.s.i. tensile load for 833 hours at room temperaturedoes not creep substantially more than 240 microinches per inch.

2. The conductor of claim 1 consisting of bare rod having a diameter ofA to 1 inch and suitable for cold drawing into wire.

3. The conductor of claim 1 consisting of cold drawn wrre.

4. An insulated conductor comprising the wire of claim 3.

5. The conductor of claim 1 consisting of a plurality of strandedcold-drawn wires.

6. An insulated conductor comprising the stranded wires of claim 5.

7. An insulated electric cable comprising a plurality V of theconductors of claim 1.

examples and description have been illustrative rather References CitedUNITED STATES PATENTS 3,063,832 11/1962 Snyder -138 3,512,221 5/1970Schoerner 75-143 X 3,515,796 6/ 1970 Schoerner 29-193 X 3,490,955 1/1970 Winter et al 75-148 X 2,075,090 3/1937 Bonsack 75-146 3,241,953 3/1966 Pryor et al. 29-193 X 3,607,151 9/ 1971 Pryor et al. 29-193 X ALLENB. CURTIS, Primary Examiner us. 01. xn.

